In the art of endless belt or roller conveyors, it is common to use a series of roller assemblies each of which includes an elongated metal roller tube supported on opposite ends by a pair of anti-friction ball bearings. The bearings are mounted by bushings on an elongated hexagonal axle which extends axially through the roller tube and has opposite end portions projecting from the tube. The axle is spring biased to a center position to permit axial movement of the axle relative to the roller tube for installing the roller assembly between horizontally spaced frame members or channels of a roller or belt conveyor having hexagonal holes within the channels to receive the end portions of the axle. One example of such a roller assembly is produced by Applicants"" assignee and shown on its Product Bulletin #102. Another example of such a roller assembly is manufactured by Ralphs-Pugh Co. and shown on a 1999 catalogue page 112. The axle or shaft extending through the roller tube may also be provided with a retractable stub axle or plunger for installing the conveyor roller between frame members, for example, as disclosed in U.S. Pat. No. 3,610,387. Other forms of roller assemblies having bearing shafts supporting retractable stub axles to facilitate installation and removal of the roller assemblies, are disclosed in U.S. Pat. No. 3,713,521 and No. 5,421,442.
With any such conveyor roller assembly, it is desirable to minimize the construction and maintenance costs of the assembly and to eliminate wear of the holes within the supporting frame members or channels. It is also desirable to provide for extending the service life of the roller assembly and for easily and quickly installing and replacing the roller assembly. In addition, it is desirable to minimize the noise level of operation of the roller assembly and to minimize the weight of the roller assembly for reducing shipping costs and simplifying roller replacement.
The present invention is directed to an improved conveyor roller assembly which is adapted for use between horizontally spaced frame members or channels of a conveyor and which provides all of the desirable features and advantages mentioned above. The roller assembly of the invention may be used for directly supporting articles to be conveyed or for supporting an endless conveyor belt which carries and transports the articles.
In accordance with one embodiment of the invention, a conveyor roller assembly includes an elongated roller cylinder or tube which may be formed of metal or extruded of an electrically conductive rigid plastics material. Each end portion of the tube receives a bearing assembly or unit which includes a tubular shaft having an outer end portion which collapses slightly to receive the inner race of an anti-friction ball bearing having an outer race confined within the end portion of the roller tube by an annular adapter or bushing. The shaft has a hexagonal bore which receives an axially moveable hexagonal stub axle and encloses a compression spring which urges the stub axle to an outer projecting position. The outer collapsible end portion of the shaft also receives in snap-fit relation an annular dust cover which protects the shaft and retains the inner race of the bearing on the shaft.
The stub axle has an inner end portion with spring tabs having cam surfaces which engage a shoulder within the shaft but permit the stub axle to be pulled outwardly from the shaft for replacement of the axle while the coil spring is retained within the shaft by the shoulder. The hexagonal stub axle has a tapered and twisted outer tip portion which extends from a slightly tapered and resilient portion to provide self-alignment and a close fit of the hexagonal stub shaft with the hexagonal hole in the adjacent frame channel. The tubular shaft, stub axle, dust cover and adaptor bushing are all molded of a glass fiber reinforced plastics material which also contains carbon to provide electrical conductivity and dissipation of any static electrical charge.
In accordance with another embodiment of the invention, the stub shaft is constructed of a slightly resilient plastics material and has an internal metal reinforcing pin, and the stub shaft is biased to its extended position by a coil spring or other spring element supported by the tubular bearing shaft which is molded integrally with the bearing dust cover. In a further embodiment, the resilient stub shafts are reinforced by opposite end portions of a cylindrical metal pin or rod which connects the stub shafts.
Other features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.